1. Field of the Invention
The present invention relates to an apparatus and a process for film deposition, and more particularly, to an apparatus and a process for depositing a film on surfaces of a flexible sheet, in particular, a lightweight rubber reinforcement sheet in a continuous and stable manner.
2. Description of the Related Art
An apparatus for depositing a film on a substrate with the use of sputtering techniques are generally divided into two groups: the “deposition-up” type and the “deposition-down” type. The substrate is positioned above a cathode in the deposition-up type, while the substrate is positioned below the cathode in the deposition-down type. In a film deposition process using sputtering, sputtered metal is re-deposited on the surface of the cathode, so that a powdered substance is peeled from the cathode when the process is continued for a prolonged time. Therefore, in the deposition-down type apparatus, the powder substance falls on the substrate to thereby cause imperfections in the deposited film, which often results in defective film deposition.
On the other hand, when the substrate is, for example, a non-woven fabric sheet, which is generally used for producing lightweight rubber reinforcements, and if the substrate is not properly treated to fix short fibers in the non-woven fabric, small fiber dust is produced during the traveling of the substrate in the apparatus. Therefore, this dust material is deposited on the surface of the target in the deposition-up type apparatus and prevents the target from performing discharge operation for a long time in a stable manner. Though such an unstable discharge can be avoided by laterally moving the traveling substrate, the use of the non-woven fabric sheet makes it difficult to horizontally travel the sheet between a pair of supporting rollers under such a condition that it remains strained, because the sheet itself lacks rigidity and thus easily slacks against the gravity
In view of the above-described problems, it is an objective of the present invention to provide an apparatus and a process for film deposition which can continuously conduct a stable film deposition for a long time without causing problems such as defective film deposition, faulty discharge and the like, even if the film is deposited to the surface of a flexible sheet such as a non-woven fabric sheet used in a lightweight rubber reinforcement.